Replace the malloc.h header with stdlib.h.

--- regexp.c.orig	Thu Nov 20 04:27:49 2014
+++ regexp.c	Thu Nov 20 04:28:00 2014
@@ -56,7 +56,7 @@ static char rcsid[] =
 
 
 #include <stdio.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <ctype.h>
 #include <string.h>
 #include "regexp.h"